Pain is by far the most frequent symptom for seeking health care. However, current understanding of pain perception lags far behind other aspects of contemporary neuroscience. Tools and techniques are equally outdated relative to other areas. As a consequence and despite many important advances the objective link between pain perception and cortical neuronal activity is still missing. Recent development of technology for multi-electrode recording in freely moving animals in conjunction with the advent of novel theoretical tools of analysis seems to provide a reasonable opportunity for uncovering the causal relationship between perception of pain and cortical neuroelectrical activity. Recent human brain imaging studies (including our own) have implicated distinct cortical patterns for acute vs. chronic pain conditions. Altogether these results suggest specific hypotheses to be tested in this project. [unreadable] [unreadable] The overall aim is to find the link between dynamic patterns of cortical activity and pain perception. Rat models of acute (transient mechanical and thermal noxious stimuli) and chronic pain conditions (peripheral partial nerve injury resultant pain behavior) will be instrumented with multi-electrode recordings. We will identify cortical spatiotemporal patterns of neuronal activity previously reported during perception in other sensory and cognitive modalities. We will test the main hypothesis that perception of pain equates to synchronous activation of multiple cortical regions on an oscillatory (Gamma-like) pattern, differing in the regions involved for acute and chronic states. Neuronal population properties to painful stimuli will be studied in awake behaving rats. Interactions within and across 5 different brain areas will be studied (primary and secondary somatosensory, insular, cingulate, and orbital frontal), using local field potentials, single- and multi-unit spike activity. Overall these results should identify the link between pain perception and cortical activity objectively enough to provide a quantitative assessment of clinical pain conditions, and propose new directions for therapy, especially for chronic pain conditions.